Hollow drum apparatus



June 30, 1964 G. D. CHENEY 3,138,848

HOLLOW DRUM APPARATUS Filed April 21, 1961 3 Sheets-Sheet l INVENTOR. 60P6 .0. (Jew/v5) A TTOIQ/VEYS June 30, 1964 G. D. CHENEY Filed April 21, 1961 HOLLOW DRUM APPARATUS 3 Sheets-Sheet 2 /a 38 l 38 {II I Il I INVENTOR. 39 60EG D. (Hm 5y BY J, 7

June 30, 1964 G. D. CHENEY 3,138,848

HOLLOW DRUM APPARATUS 3 Sheets-Sheet 3 Filed April 21, 1961 JLM.

United States Patent 3,138,843 H'GLLQW DRUM APPARATUS George D. Cheney, Orchard Lake, Mich, assignor to IEx-Cell-O Corporation, Detroit, Mich. Filed Apr. 21, 1961, Ser. No. 1tl4,663 14 Claims. (Cl. 29-123) systems, such as computers, data processing machines,

automatic controls for machine tools, and the like, where it is frequently necessary to store information in the socalled memory part of the apparatus for use at a later are in extensive use for the memory part of the apparatus, as is well known to those skilled in the art. Drums of this type are generally made of a non-magnetic substantially cylindrical body coated with a thin layer of magnetizable material. The drum rotates, often at high and constant speed, within a housing on which are fastened one or more rows of magnetic transducer heads. The magnetic heads are used for sequentially writing signals on the magnetizable surface of the drum, for reading signals, or for bothwriting and reading signals.

The spacing of the magnetic heads from the magnetizable surface on the drum is critical and must be maintained practically constant inspite of distortion of the drum and'housing due to thermal expansion, as well as V eccentricity, wobble, vibration, runout of the rotating parts, etc. The. drum is a statically and dynamically balanced high-precision component having critical dimensions, and must be supported in its housing by highquality bearings in order to prevent eccentricity, vibration, runout and wobble.

Another troublesome phenomenon is the appearance of centrifugal growth due to the action of centrifugal force upon a body rotating at high velocity. The drum, being often'a hollow metal cylinder attached to a shaft by means of flanges or spokes, will not remain, a true cylinder at operational speed because the unsupported portion of the cylindrical body tends to grow more than the portions, generally the end portions, which are partly restrained against centrifugal growth by the coercing action of the flanges .or spokes. Such an uneven centrifugal growth, resulting in a barrel-shaped drum at operational speed, is a shortcoming in drums used in magnetic recording apparatus, due to'the requirement that the air gap between the respective transducer. heads pole pieces along the length of the drum and the magnetizable surface on the drum be nonuniform in order to provide for an even air gap for all the heads when the drum has reached normal rotational speed. Another way of compensating 'for the uneven centrifugal growth would be by machining thedrum with a diameter decreasing toward the midsection instead of machining the drum as a true cylinder; by calculation and by experimentation, a formula could be established determining the profile to give to the drum time when such information is required. Rotating drums so that it will become a true cylinder at operational speed.

Sucha method is tedious and costly, and the object of the present invention is to provide a hollow precision rotating drum being built in such a way as to cause the drum to remain a true cylinder at a high rotational speed as well as at rest. 1

'drical body 14.

3,138,848 Patented June 30, 1964 Another object of the present invention is to provide a hollow drum having a centrifugal growth which is constant all along its peripheral length, irrespective of the rotationalvelocity of the drum surface.

Still another object of the invention is to fabricate a drum of a few simple components which are easy to manufacture and to assemble, instead of being made of a complex casting or forging diflicult to machine.

A further object of the invention is to provide a hollow drum which is light but strong, instead of being made of a massive and heavy solid cylinder of material.

A still further object of the invention is to obtain a composite drum which requires no complex fastenings for the assembly of the component parts other than cementing, press-fitting, or fitting by. shrinkage of the elements upon one another.

Additional objects and advantages of the invention will become apparent from the following description and appended claims, taken in connection with the accompanying drawings, which disclose the principles of this invention and some of the best modes which have been contemplated of applying these principles.

In the drawings:

FIG. 1 represents a sectional view taken substantially along the longitudinal axis of one embodiment of the present invention; 7

FIG. 1a is a diagrammatical view of some of the elements shown in FIG. 1, to illustrate the principlesof the invention; I

FIG. 2 is a sectional view similar to FIG. 1, but representing a modification of the present invention;

FIG. 3 is a sectional view similar to FIGS. 1 and 2, but representing a further modification of the present invention;

FIG. 4 is a sectional View taken along line 4-4 of FIG. 1; 7

FIG. 5 is a'sectional view similar to FIG. 4, but showing an alternative construction of the invention; and

FIG. .6 is a sectional view similar'to FIG. 4, but showing another alternative construction of the invention.

With reference now to the drawings, wherever like or corresponding parts are designated by the same reference numerals through the several views, FIG. 1 illustrates an example of a rotating drum constructed in accordance with the present invention. A cylindrical drum MB is shown contained within a housing 12 for illustrative purposes only. Thedrum which is preferably, but not necessarily, an aluminum, aluminum alloy, magnesium or magnesium alloy hollow cylindrical body 14 is fastened upon a shaft 16 by the intermediary of first end wall 18 and second end wall 20. The shaft 16 is rotatable within the housing 12 by being supported therein by bearing means such as the ball bearings 22 and 24.

End wall 2% is integral with cylinder 14 and has a bore 26 provided along the center line therein. This bore may be slightly smaller than the corresponding diameter of shaft 16 in order to permit assembly of the components by shrink fit or press fit. End Wall 18 is similarly constructed with a bore 30 which can be shrink or press fitted upon diameter 32 of shaft 16. The outer diameter 34 of end wall llfiis also shrink or press fitted within the undercut inner shoulder portion '36 of cylin- If so preferred, the component parts may also be cemented or bonded together by synthetic adhesives, such as those of the epoxy class.

V The surfaces of end walls 18-20 are conical and parallel, and make an angle oc with the radius of the axis of 'rotation'of the drum, for the reasons given hereinafter.

End wall 18 has apertures cut out as indicated in FIGS. 4-6, leaving only the spoke portions 38 between the hub portion 40 and the outer ring portion 42. End wall 20 is similarly constructed with integral spokes 38 connecting its'hub portion -44 with the cylindrical drum 14.

The spokes are radially disposed and their number may vary as shown in the examples of FIGS. 4 and 5, or they may be the remaining material left after slots such as 39. (FIG. 6) have been machined radially in the end walls 18-20.

In the modifications of FIG. 2, the drum is constructed in a similar fashion, with the exception of end wall 20. Instead of being integral with drum cylinder 14, end wall 20 has its outer ring portion 46 press-fitted, shrinkfitted or bonded to the undercut inner shoulder portion 48 of drum cylinder 14, and ring portion 46 is preferably wider than ring portion 42 of end wall 18, the coacting shoulder portion being wider so as to fit properly. In the embodiment of FIG. 3, end wall 20 has its outer ring portion 46 further presenting a step-like abutment portion 47 which facilitates assembly and allows the drum cylinder 14 to have undercut inner shoulder portions of identical lengths on both its ends.

. When a drum constructed according to the principles of the invention is rotated at high speed, the unsupported mid-section of the cylindrical body increases in diameter becauseof centrifugal growth. The spokes supporting the ends of the cylindrical body are deflected, under the action of the centrifugal force, toward the true radius of the drum. This deflection increases the effective diameter of the ends of the cylindrical body, and by a proper selection of both the spokes cross-section area and the angle cc between the spokes centerline and the radial plane of. the drum, the effective centrifugal growth of the cylindricalbody ends can be controlled to be made equal to that of the cylindrical body unsupported midsection.

I With end Walls of the types illustrated in FIGS. 45, the amount of centrifugal growth of each individual spoke is determined by a formula which is substantially of the form:

in which'A denotes the cross-section area of the spoke, p denotes the density of the material constituting the spoke, a: is the rotational velocity in revolutions per second, E is the modulus of elasticity of the spoke (Young modulus), I is the moment of inertia of the spoke, and R and R are the radii as shown in FIG. 1a.

With end walls of the type illustrated in FIG. 6, the formula giving the growth 2 of one spoke is substantially similar to the formula above with the exception that the 7 terms A and I are variable and must be integrated to obtain a value taking into consideration the variations of cross-section area and moment of inertia of the spoke from its root to its tip.

In the threepreferred embodiments herein illustrated, the drum is shown as being surrounded by a housing 12 for illustrative purposes only. It is obvious to those skilled in the art that such would generally be the case in a magnetic drum used in the memory part of a data processing machine, computer, or the like, but it is contemplated that a hollow drum constructed according to the principles of this invention would have numerous advantages in other diverse applications.

Evidently, many modifications and variations of the present invention are possible in the light of the above teachings. It is apparent that changes may be made in the form of the apparatus disclosed without departing from the scope and spirit of the invention as set forth in the appended claims, and that in some cases, certain features of the invention may be used to advantage without a corresponding use of other features.

7 Having now described the invention, what is claimed as new is: i

1. A rotatable drum comprising: a hollow cylindrical body member having an undercut inner shoulder portion on one end; a. shaft disposed within the cylindrical body member substantially concentrically about the 1011- gitudinal centerline therein; two conical substantially parallel end walls fastening the cylindrical body member to the shaft, one of said end walls being an integral part of said cylindrical body member and the other end wall being secured to said undercut inner shoulder portion, said conical end Walls having apertures defining spokes disposed at an angle with true radii of the cylindrical body member, whereby rotation of the drum deflects said spokes in the same direction toward the radii of the cylindrical body member allowing the ends of said body member as well as the portion intermediate said ends to be expanded by centrifugal force. I

2. A drum as claimed in claim 1 in which the apertures in the end walls define substantially identical spokes of substantially constant cross area from end to end.

3. A drum as claimed in claim 1 in which the apertures in the end walls are substantially radial slots having substantially constant cross section area from end to end.

4. A rotatable drum comprising: a hollow cylindrical body member having undercut inner shoulder portions on both its ends; a shaft disposed within the cylindrical body member substantially concentrically about the longitudinal centerline therein; two conical substantially parallel end walls fastening the cylindrical body member to the shaft being secured to said undercut inner shoulder portions; said conical end walls having apertures defining spokes disposed at an angle with true radii of the cylindrical body member, whereby rotation of the drum deflects said spokes in the same direction toward the radii of the cylindrical body member allowing the ends of said member as well as the portion intermediate said ends to be expanded by centrifugal force.

5. A drum as claimed in claim 4 in which the apertures in the end walls define substantially identical spokes of substantially constant cross area from end to end.

6. A drum as claimed in claim 4 in which the apertures on the end walls are substantially radial slots having substantially constant cross area from end to end.

7. A rotatable drum comprising: a hollow cylindrical body member having undercut inner shoulder portions on both its ends; a shaft disposed within the cylindrical body member substantially concentrically about the longitudinal centerline therein; two conical substantially parallel end walls fastening the cylindrical body member to the shaft secured to said undercut inner shoulder portions, one of said end walls having its perimeter presenting a step-like abutment portion adapted to project beyond the end face of said cylindrical body member parallel to said end face and in contact therewith; said conical end walls having cutout apertures defining spokes disposed at an angle with true radii of the cylindrical body member, whereby rotation of the drum deflects said spokes in the same direction toward the radii of the cylindrical body member allowing the ends of said member as well as the portion intermediate said ends to be expanded by centrifugal force.

8. A drum as claimed in claim 7 in which the apertures in the end walls define substantially identical spokes of substantially constant cross area from end to end.

9. A drum as claimed in claim 7 in which the apertures on the end walls are substantially radial slots having substantially constant cross area from end to end.

10. A rotatable drum comprising: a hollow cylindrical body; a shaft disposed 'within the cylindrical body about the longitudinal axis thereof; two substantially equidistant conical end walls to support the cylindrical body on both its ends; said conical end walls having a plurality of apertures defining spokes therein; and means fastening the end walls to the shaft and to the cylindrical body.

11. A rotatable drum as claimed in claim 10 wherein the means fastening the end walls to the shaft and to the cylindrical body is a bonding cement.

12. A rotatable drum as claimed in claim 10 wherein the means fastening the end walls to the shaft and to the cylindrical body comprises at the respective points a press fit.

13. A rotatable drum as claimed in claim 10 wherein the means fastening the end walls to the shaft and to the cylindrical body comprises at the respective points a shrink fit.

14. A rotatable drum comprising: a tubular cylindrical body member; a shaft disposed within the tubular member along the longitudinal axis thereof; spoke members in substantially parallel planes supporting the ends of the tubular member in spatial relationship substantially concentrically to the shaft; means fastening the spoke members to the inner surface of the ends of the tubular member; means fastening the spoke members to the shaft; each of said spoke members having its centerline' at an angle with the radius of the tubular member, whereby rotation of the drum deflects each of said spokes in the same direction toward the radius of said tubular member in such a way as to permit said tubular member to expand substantially constantly along its periphery under the effect of centrifugal force.

References Cited in the file of this patent UNITED STATES PATENTS 

10. A ROTATABLE DRUM COMPRISING: A HOLLOW CYLINDRICAL BODY; A SHAFT DISPOSED WITHIN THE CYLINDRICAL BODY ABOUT THE LONGITUDINAL AXIS THEREOF; TWO SUBSTANTIALLY EQUIDISTANT CONICAL END WALLS TO SUPPORT THE CYLINDRICAL BODY ON BOTH ITS ENDS; SAID CONICAL END WALLS HAVING A PLURALITY OF APERTURES DEFINING SPOKES THEREIN; AND MEANS FASTENING THE END WALLS TO THE SHAFT AND TO THE CYLINDRICAL BODY. 